The two are different technologies and have different applications, which sometimes overlap. The big difference between the two is bar codes are line-of-sight technology.

That is, a scanner has to "see" the bar code to read it, which means people usually have to orient the bar code toward a scanner for it to be read. Radio frequency identification, by contrast, doesn't require line of sight. RFID tags can be read as long as they are within range of a reader. Bar codes have other shortcomings as well.

If a label is ripped or soiled or has fallen off, there is no way to scan the item, and standard bar codes identify only the manufacturer and product, not the unique item.

The bar code on one milk carton is the same as every other, making it impossible to identify which one might pass its expiration date first.